1. Field of Invention
The invention relates to near field communications (NFC), and more specifically to detecting a presence of a NFC capable device.
2. Related Art
Near field communication (NFC) devices are being integrated into mobile devices, such as smartphones for example, to facilitate the use of these mobile devices in conducting daily transactions. For example, instead of carrying numerous credit cards, the credit information provided by these credit cards can be loaded into a NFC device and stored therein to be used as needed. The NFC device is simply tapped to a credit card terminal to relay the credit information to it to complete a transaction. As another example, a ticket writing system, such as those used in bus and train terminals, may simply write ticket fare information onto the NFC device instead of providing a paper ticket to a passenger. The passenger simply taps the NFC device to a reader to ride the bus or the train without the use of the paper ticket.
Generally, a NFC interaction includes a polling mode of operation to establish a communication among NFC devices. A first conventional approach probes a magnetic field of a first conventional NFC device for a second NFC device in accordance with a predefined polling routine. In this first conventional approach, the first conventional NFC device generates the magnetic field without any information for a predetermined duration, typically referred to as a guard time, that is technology dependent. The first conventional NFC device then probes the magnetic field for a second NFC device of a first technology type, such as type A, type B, or type F to provide some examples, using a conventional polling command upon expiration of the guard time. The conventional polling command includes such a conventional request command, type A (REQA), a conventional request command, type B (REQB), or a conventional request command, type F (REQF). The first conventional NFC device then generates the magnetic field without any information for another guard time and probes the magnetic field for a second NFC device of a second technology type using the conventional polling command if no response is received from the second conventional NFC device. The first conventional approach is further described in “NFC Forum: NFC Activity Specification: Technical Specification, NFC Forum™ Activity 1.0 NFCForum-TS-Activity-1.0,” published Nov. 18, 2010, which is incorporated by reference herein in its entirety.
The guard time of the first conventional approach unnecessarily consumes power. Typically, the guard time is approximately 5 ms when probing for type A and type B NFC devices and may reach more than 20 ms when probing for type F NFC devices. Additionally, the first conventional NFC device may have to generate the magnetic field without any information for more than one guard time and probe the magnetic field using more than one polling command for certain technologies. For example, the first conventional approach typically polls for type A devices then for type B devices which is followed by type F devices. In this example, the first conventional NFC device generates the guard time for type A, B, and F devices and provides the REQA, REQB, and REQF commands to establish a communication with a type F NFC device.
A second conventional approach transmits detection pulses having substantially similar magnitudes to detect a presence of NFC devices. A first NFC device continuously provides the detection pulses until a change in the magnitude one of the detection pulses is detected. This change is indicative of a second NFC device being present within a magnetic field of the first NFC device. The second conventional approach is further described in U.S. patent application Ser. No. 12/446,591, filed on Apr. 22, 2009 under 35 U.S.C. §371(c), which is incorporated herein by reference in its entirety.
However, this simple detection of pulse change is susceptible to changes in environment. For example, moving the first NFC device around the environment may cause the magnitudes of the detection pulses to change. As another example, objects within the environment, such as metal objects or other non-NFC capable devices to provide some examples, entering into the magnetic field may cause the magnitudes of the detection pulses to change. These changes may result from changes in the environment alone and, not from the second NFC becoming present within the magnetic field. Consequentially, the first NFC device may improperly determine that the second NFC device is present.
Thus, there is a need to detect a presence of another NFC device within a magnetic field that overcomes the shortcomings described above. Further aspects and advantages of the present invention will become apparent from the detailed description that follows.
The invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the reference number.